Per MLB.COM
Tanner Houck, RHP, Red Sox
Key stat: +2.2 mph of fastball velocity, +2 inches of slider movement
Houck is currently at the Red Sox's alternate training site because they needed roster flexibility, but the 24-year-old's pitching during Opening Week was more than big league-caliber -- he has 10 strikeouts in six innings so far in 2021.
Boston's No. 7 prospect per MLB Pipeline was nasty in his brief debut stint in 2020, too, but his stuff got even better. Houck is throwing 2 mph harder in '21 than he did in '20 -- his four-seam velo has jumped from 92.8 mph to 94.6, and his sinker velo has jumped from 90.9 mph to 93.7, giving him an overall velocity spike of +2.2 mph.
Houck's wipeout, crossfire slider is moving even more, with his average horizontal break up to 15.9 inches from 13.9 in 2020. That break is a huge +9.2 inches above average, when you compare Houck's slider to similar ones based on velocity and release point. And Houck is getting the most out of it, throwing his slider 42% of the time so far, his most-used pitch type. With that stuff, he'll be back soon.
Sure looks like he's first one up if someone falters.